Optimization of power consumption has become an increasingly important factor in circuit design and product development. Many differing techniques have emerged to reduce power consumption within electronic devices, and many of these techniques are directly related to the physical properties of circuits in the electronic devices. For example, techniques for reducing feature size, such as the size of transistor channels, and reducing operating voltages have yielded large power reductions for integrated circuits during recent decades.
Dynamic techniques applied after the device is powered and operational, such as differing modes of operation and time sequencing of functions, reduce power consumption during inactive periods. For example, most portable devices include processors that support a sleep mode where power is conserved when the user is not using the device. For radio frequency-based devices, instead of continuously listening for a signal, signal detection circuits operate on a periodic basis to conserve power, and the devices switch to a continuous operating mode when appropriate signals are detected. More recent dynamic power control techniques involve scaling the clock frequency and supply voltage of circuits for matching power consumption to the computational demands placed on the device.
Most commonly, a power switch, which may include a mechanical device disconnecting circuitry from a power source, is used to conserve power. All of these techniques may be used to conserve power. However, in almost all of these techniques the device remains powered in some form throughout its operation, even if the majority of the device is functionally disabled or de-powered. Even if a power switch is used, the device is susceptible to loss through leakage current. Furthermore, power switches are typically mechanical and are susceptible to wear. Also, mechanical power switches require physical or contact-based user interaction to enable or disable a device.